Screening for diseases with molecular defects in protein C receptor

内皮细胞蛋白C受体（EPCR）对血浆抗凝蛋白C具有特异性的高亲和力结合。蛋白C作为丝氨酸蛋白酶的酶原形式循环，在内皮细胞表面转化为活性形式的酶时起抗凝作用。已发现凝血酶/凝血调节蛋白（TM）复合物介导了活化的催化反应。我们发现，通过转染细胞系和功能阻断型抗EPCR单克隆抗体，EPCR极大地加速了复合物介导的蛋白C激活。在生理条件下，EPCR似乎是蛋白C激活所必需的，因此，该分子的功能或表达异常可能导致凝血缺陷。我们发现在胶质母细胞瘤和单细胞白血病患者建立的细胞系中诱导了功能性EPCR。急性粒细胞白血病M4型和M5型患者外周血单个核细胞（PBMC） EPCR阳性。相比之下，来自健康供者的PBMC对抗原呈阴性。EPCR可能成为某些类型癌症的新标志物，该分子的异常表达可能解释癌症中某些凝血障碍。我们还开发了一种筛选系统来检测EPCR的遗传缺陷。我们建立了扩增EPCR外显子的PCR方法，也建立了直接测序方法。目前正在使用这些方法进行筛选。

The endothelial cell protein C receptor (EPCR) is capable of high-affinity binding specific for plasma anticoagulant protein C.Protein C circulates as a zymogen form of serine protease and functions as an anticoagulant when is converted to active form of enzyme on the endothelial cell surface. The thrombin/thrombomodulin (TM) complex has been found to mediate the catalytic reaction for the activation. We found that EPCR greatly accelerated protein C activation mediated by the complex by using transfected cell lines and function blocking anti-EPCR monoclonal antibodies. EPCR appears to be essential for protein C activation under the physiological conditions, therefore, abnormal function or expression of this molecule might cause defects in blood coagulation. We found that functional EPCR was induced in several cell lines established from glioblastoma and monoblastic leukemia patients. Peripheral blood mononuclear cells (PBMC) from patients with acute myerocytic leukemia type M4 and M5 were also positive for EPCR.In contrast, PBMC from healthy donors were negative for the antigen. EPCR could be a novel marker for some types of cancers, and abnormal expression of this molecule might explain some disorder of blood coagulation in cancer. We also developed a screening system to detect the genetic defects of EPCR.We established PCR methods to amplify the exons of EPCR and also established direct sequencing methods. Screening by using these methods is now under going.